Systematics of the oil bee genus Lanthanomelissa (Apidae: Tapinotaspidini) and its implications for the biogeography of South American grasslands

Lanthanomelissa has an uncertain taxonomic history, and was formerly treated either as an independent genus or as a subgenus of Chalepogenus. It is endemic to southern South American grasslands, an endangered and poorly known environment. We aimed to understand the origin of these bees in time and space, the influence of Quaternary climatic fluctuations on their current distribution, and the possible link to the southern South American grasslands’ history. We inferred phylogenetic relationships in Lanthanomelissa using 37 specimens from all six species and 3430 nucleotides of three mitochondrial and two nuclear genes and estimated divergence times and ancestral geographic range. We modeled species distribution for the current and two past climatic scenarios (LIG, ~120 kya, and LGM, ~21 kya), performing an ensemble with three algorithms in a dataset of 192 georeferenced occurrence points using 19 WorldClim bioclimatic variables. The results support the monophyly of the genus and taxonomic changes, including the species Lanthanomelissa parva n. comb., and the treatment of the goeldianus group of Chalepogenus as the genus Lanthanella. Lanthanomelissa originated at the Oligocene–Miocene border in the Chacoan–Pampean region, and the glacial–interglacial models indicate expansion in the Last Glacial Maximum and retraction in the Last Interglacial. This origin was approximately synchronized with their exclusive floral host, Sisyrinchium (Iridaceae). The diversification of Lanthanomelissa supports the estimated austral expansion of the ancestral southern grasslands in South America before the origin of Cerrado during the late Miocene. Expansion and retraction in distribution during the last glacial–interglacial indicate grasslands distributional shifts through climate cooling and warming periods. Resumo A posição taxonômica das abelhas do gênero Lanthanomelissa é controversa, sendo tratadas tanto como um gênero independente ou como um sugênero de Chalepogenus. Estas abelhas são endêmicas dos Campos Sulinos na América do sul, um ecossistema ameaçado e pouco estudado. Neste contexto, este trabalho tem como objetivo estudar a origem de Lanthanomelissa no tempo e espaço, a influência das flutuações climáticas do quaternário na sua distribuição atual e suas possíveis relações com a história biogeográfica dos Campos Sulinos. Nós inferimos as relações filogenéticas em Lanthanomelissa usando 37 espécimes de todas as seis espécies e 3430 nucleotídeos de três genes mitocond